1. Field of the Invention
This invention generally relates to flexible composite materials which are extremely heat-resistant, and methods of making same, which materials have a continuous layer or coating of solid film lubricant or glass release agent which essentially comprises an organic-inorganic silicone resin having a finely-ground particulate filler therein. The layer or coating is formed by taking an essentially solventless organopolysiloxane resin or mixture of such resins and dispersing a prescribed amount of finely-ground particulate material therein, the combined materials being applied to and heat cured on a woven fibrous substrate comprised of a polymeric thermoset material such as polyaramid fibers or similar high-temperature resistant substrates. The selected substrate after coating may be severed into precisely-sized and shaped contours prior to or subsequent to heat-curing the resin containing the filler material.
The composite material may be fabricated into conveyor belting, sweep arm covering, tong liners, and the like, for handling newly-formed hot glass articles without marring their surfaces or creating objectionable emissions from the composite material due to excessive heat. The coating cures into a thermoset hardened condition on the substrate surface while permitting the substrate to retain an appreciable degree of flexibility. Normally, the polymeric fibrous substrate, while possessing an appreciable amount of heat resistance, cannot be employed alone without a suitable heat-resisting coating for long-term repeated handling of hot glass articles.
2. Description of the Prior Art
It has been common practice in the glass forming art to fabricate or cover conveyor belts for transporting hot glass articles with asbestos or asbestos-containing materials such as transite to provide heat-resistant surfaces which would not mar the glass and provide long-term operating life. Also, bucket liners and sweep arm fingers have previously been fabricated with coverings of asbestos cloth for handling hot glass articles.
In the production of glassware, certain handling equipment has also been coated with graphite and petroleum oil swabbing compositions to provide lubricity and heat-resistance. In the use of such coatings, when the petroleum fraction flashes off, it can detract from effective lubrication during forming.
The use of water-based carriers instead of the petroleum oil carriers for graphite and other lubricous materials have not been entirely satisfactory primarily due to the high heat of vaporization of water and the resulting excessive cooling of the glass-handling equipment. In addition, it is difficult to controllably wet the handling equipment surfaces with water-based materials which are applied intermittently during production of glassware.